1. Field of the Invention
The present the invention relates to the molding of containers for liquid and viscous products.
2. Description of Related Art
Plastic containers are commonly used for the packaging of various products, including liquid products and viscous products. One of the most common forms of plastic container is the blow molded plastic container, which are often formed of polyester materials and, more specifically, of polyethylene terephthalate (PET). Blow molded plastic containers are generally formed by placing a heated preform into a blow mold and then inflating the preform with air until the preform contacts the interior surfaces of the mold cavity, which define the final shape of the desired container. Once the inflated preform has been positively held against the interior surfaces of the mold cavity for a length of time sufficient to “freeze” the plastic, the molded container is removed from the mold.
Molded containers are then transported to a location where the container will be filled with the intended product and labeled. This post-molding process may include the packaging and shipping of the container to a different physical location or may involve the transferring of the container to another location in the manufacturing facility where these final steps are performed.
In an effort to reduce costs and decrease materials ultimately entering into landfills, the amount of material in these containers has been reduced. As a consequence, the containers are less strong, and such non-carbonated containers can experience a collapsing of the container's sidewall when stacked because of the top-load applied thereto.
One method to increase the top-load strength of a container is to dose the container with nitrogen immediately prior to final sealing and capping of the container. By introducing nitrogen into the headspace of the container, the content volume and internal pressure of the container is increased. The increased pressure displaces the liquid located below the headspace, which in turn results in an increase in the top-load strength of the container.
Nitrogen dosing, however, is costly and therefore can negatively affect the economics of the category of the product in the container. For example, bottled water has lower profit margins than other bottled liquids, but water containers are one of the containers most impacted by light weighting due to the sheer number of water bottles that enter the product stream. Nitrogen dosing reduces that margin even further.
A newer process for forming containers involves the use of the end product itself as the medium for molding the container. During this process, the container is simultaneously molded by and filled with the end product. As used herein, this molding technique is referred to as hydraulic molding.